Seat and backrest for a chair



FIG. 1 is a perspective view showing the top, left side and front of a seat and backrest for a chair which form my new design, the broken lines of other parts of the chair being for illustrative purposes only and forming no part of the claimed design;

FIG. 2 is a left side elelvational view thereof;

FIG. 3 is a right side elevational view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a rear elevational view thereof; and,

FIG. 6 is a top plan view thereof. 

The ornamental design for a seat and backrest for a chair, as shown and described. 